1. Field of the Invention
This invention relates to an air conditioner system and, more particularly, to an air conditioner system including a plurality of variable-capability compressors.
2. Description of the Related Art
As a multi-type air conditioner system constituted by a heat pump type refrigeration cycle, an air conditioner system including a plurality of devices for the refrigeration cycle such as an outdoor unit having a plurality of variable-capability compressors, and a plurality of indoor units, for controlling the number of operating compressors and their operating frequency in accordance with a required capability of each indoor unit, is conventionally known.
In such an air conditioner system, the higher-side pressure of the refrigeration cycle is often increased to an abnormal level upon starting under an overload condition. Therefore, in this condition, the devices for the refrigeration cycle are adversely affected.
A high pressure switch operated at a predetermined pressure is provided in the refrigeration cycle, for interrupting the operation of the air conditioner system, thus protecting the devices against high pressures.
In order to minimize the number of instances of interruption of the operation of the air conditioner system, a so-called frequency-reduction release for reducing the operating frequency of the compressor is performed when the higher-side pressure reaches a preset value slightly lower than the point at which the high pressure switch is activated, in order to suppress any further increase in the higher-side pressure.
However, when an oil-equalizing operation between the compressors is performed upon starting of the system, or when a small number of indoor units begin operating, the higher-side pressure increases rapidly, with the result that the frequency-reduction release cannot respond an increase in the high-side pressure. As a result, the high pressure switch is operated, interrupting the starting operation of the air conditioner system.
The interruption because of the above-described reason is not necessarily preferable for a user. It is preferable for the user that the air conditioner system avoids interruption of the starting operation, and smoothly reaches a normal operation.